1. Field of the Invention
The present invention relates to the field of device sterilization and, in particular, to the sterilization of in vivo medical devices.
2. Description of Related Art
Device sterilization is a routine and necessary step in the manufacture of products in the medical, pharmaceutical, plastic, cosmetic and food industries as well as other industries. Device sterilization facilitates aseptic introduction of a device into its intended environment. For example, in the field of medical devices, where some devices may be used in sterile environments such as, for example, operating rooms or where some devices may be utilized in vivo, such as, for example, physiological parameter sensors, device sterilization aids in the elimination of deleterious microorganisms from the human body environment, reducing the risk of infection and disease.
Traditional device sterilization has been performed in a variety of ways. For example, in the medical device area, ethylene oxide (EtO) sterilization has been an effective sterilant for the elimination of microorganisms from medical devices. Being a gas, EtO may permeate an entire structure, resulting in three-dimensional sterilization of a device. However, EtO is a highly toxic gas and can have a damaging effect on certain products. For example, biosensors typically utilize a biomolecule as a sensing element. Exposure of a biomolecule to EtO may substantially reduce the long-term stability and sensitivity of the biomolecule, making EtO undesirable as a sterilant for biomolecular sensing elements.
Other sterilants are also available and in wide use for device sterilization. For example, glutaraldehyde is used extensively as a disinfectant for equipment in the medical and dental industries. Glutaraldehyde is commonly supplied as an aqueous solution and, when used as such, provides for bulk sterilization of equipment. In addition, if the device being sterilized is a biosensor having a biomolecule as a sensing element, glutaraldehyde typically does not produce any damaging effects on the biomolecule. However, being supplied as an aqueous solution, glutaraldehyde, as well as other aqueous sterilants, may not be able to permeate portions of devices that have been sealed for protection. For example, if a portion of a sensor houses electronics, the electronics may be enclosed in a housing impervious to fluids so that introduction of a fluid to the electronic housing does not result in the short circuiting of the electronics. In such a situation, glutaraldehyde or other aqueous sterilants are ineffective to sterilize the device.
When gaseous or liquid sterilants have proven ineffective to sterilize the devices in question, industry has turned to other methods of sterilization. For example, radiation sterilization using gamma or electron-beam radiation is sometimes effective but can destroy sensitive components upon application. For example, radiating devices that contain integrated circuits that have not been radiation hardened may damage the integrated circuits, rendering the devices inadequate for their intended purposes.
Steam sterilization may also be sometimes effective, but devices being sterilized by steam must be able to withstand high temperatures and condensation that are a natural byproduct of the steam process. Many devices cannot withstand such an environment.